Cancerous or benign lesions of the gastro-intestinal (GI) tract often start in the mucosal layer of the stomach or intestines. With improved diagnostics and screening, such lesions are generally identified before they affect the stomach and/or the intestines. Treatments and therapies for treating lesions have involved invasive surgical resection of the affected tissue or lesion. Early identification and treatment of such lesions, through methods including local excision of the mucosa, accessed via natural orifices, may be preferred as they are less invasive.
An example of a less invasive technique for treating tissue defects or lesions, including conditions related to varices, chronic liver disease, hemorrhoids, and the like, is band ligation. In band ligation, the affected or target tissue is bound with a band to form a pseudo polyp, thus establishing a ligated tissue. The ligated tissue may be removed using a removal device, such as a snare.
For band ligation, the band is delivered into the body as part of a ligation unit or device, which is configured to be steered and positioned adjacent the target tissue. Typically, ligation units are inserted into natural body cavities or through an incision, at a distal end of an endoscope.
In some ligation units, ligation bands may be tightly arranged over a cap-like structure, and deployed over the target tissue. Strings or sutures may be employed to advance the bands towards a distal end of the device to release the bands from the ligation unit. In some cases, portions of the band may slide along the surface of the cap, instead of rolling along the surface of the cap. Such a situation may lead to a twisted, angular, inverted, and/or otherwise undesirable deployment of the band, causing the tissue to be held improperly. For example, the band may fail to compress the tissue appropriately when deployed, causing the formation of a necked or otherwise misshaped polyp, or causing an increase in the risk of perforating underlying tissue layers.
To address such conditions, surface features can be provided on the cap-like structure to engage the bands during their deployment. Such surface features may, however, limit visibility through and around the cap-like structure, depending on their characteristics.